I always thought speaking in tongues was just some kind of hysterical ranting. I did a bit of reading and it's mostly a learned behaviour that has no real meaning other than conforming to social norms.

No. I went to church when I was a teen once and "spoke tongues", to see if I could, and did so effortlessly even though I'm an Atheist. Tongues theory debunked. Does not require belief in God or Jesus, it's proof of nothing except how silly people are.

There were some crazy priests (this is maybe an urban legend) that closed of boys so that they could not see the sun and so that they could not hear anyone speak because they believed that they will start to speak but with one true language, god's language, because god gave us language according to the bible. But what happened is that the boy started to die because they didn't have enough vitamin D because of lack of sun (we now know that, they of course didn't know this then).